We are climbing rainier in late July (via the Kautz route). We have an extra day after the hike and would like to do another hike. We'd like to do Adams but looks like an almost four hour drive from ashford. Is this doable? Our plan would be to drive to the adams area the night before and do the south climb. 10 hours a reasonable hike time estimate?

South side of Adams is a long haul on crappy roads. At least 4 hours from Ashford. The thing to consider is how you will be feeling after climbing Rainier. Kautz route is not the easiest or shortest route on Rainier and most climbers are fairly gacked after doing any route. If you allow yourself a full rest day you might feel up to doing another climb. 10 hours on the South Spur might be a good target if you are a fast climber.